Metal-o-Turtle, known as Dokabuton (ドカブトン) in Japan, is a variety of Badnik created by Dr. Eggman, encountered by Sonic and Tails in Gigalopolis Zone during Sonic Chaos.
Despite their name from the US and European manuasl, Metal-o-Turtles resemble large robotic stag beetles. They have no proactive offense; they simply drive back and forth, damaging Sonic/Tails if he bumps into them. Metal-o-Turtles are easily dispatched by a Spin Attack.
Like other robots in 8-bit Sonic games, no animal friends pop out of Dokabutons when they are destroyed. Whether these Badniks canonically don't contain organic batteries, or the escaping critters simply weren't shown due to programming limitations, is not known.